Ecology Letters (2011)
Soaring birds migrate in massive numbers worldwide. These migrations are complex and dynamic phenomena, strongly influenced by meteorological conditions that produce thermal ...and orographic uplift as the birds traverse the landscape. Herein we report on how methods were developed to estimate the strength of thermal and orographic uplift using publicly available digital weather and topography datasets at continental scale. We apply these methods to contrast flight strategies of two morphologically similar but behaviourally different species: golden eagle, Aquila chrysaetos, and turkey vulture, Cathartes aura, during autumn migration across eastern North America tracked using GPS tags. We show that turkey vultures nearly exclusively used thermal lift, whereas golden eagles primarily use orographic lift during migration. It has not been shown previously that migration tracks are affected by species‐specific specialisation to a particular uplift mode. The methods introduced herein to estimate uplift components and test for differences in weather use can be applied to study movement of any soaring species.
plausible model of phyllotaxis Smith, R.S; Guyomarc'h, S; Mandel, T ...
Proceedings of the National Academy of Sciences - PNAS,
01/2006, Letnik:
103, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A striking phenomenon unique to the kingdom of plants is the regular arrangement of lateral organs around a central axis, known as phyllotaxis. Recent molecular-genetic experiments indicate that ...active transport of the plant hormone auxin is the key process regulating phyllotaxis. A conceptual model based on these experiments, introduced by Reinhardt et al. Reinhardt, D., Pesce, E. R., Stieger, P., Mandel, T., Baltensperger, K., et al. (2003) Nature 426, 255-260, provides an intuitively plausible interpretation of the data, but raises questions of whether the proposed mechanism is, in fact, capable of producing the observed temporal and spatial patterns, is robust, can start de novo, and can account for phyllotactic transitions, such as the frequently observed transition from decussate to spiral phyllotaxis. To answer these questions, we created a computer simulation model based on data described previously or in this paper and reasonable hypotheses. The model reproduces, within the standard error, the divergence angles measured in Arabidopsis seedlings and the effects of selected experimental manipulations. It also reproduces distichous, decussate, and tricussate patterns. The model thus offers a plausible link between molecular mechanisms of morphogenesis and the geometry of phyllotaxis.
Movement Ecology of Migration in Turkey Vultures Mandel, J. T.; Bildstein, K. L.; Bohrer, G. ...
Proceedings of the National Academy of Sciences - PNAS,
12/2008, Letnik:
105, Številka:
49
Journal Article
Recenzirano
Odprti dostop
We develop individual-based movement ecology models (MEM) to explore turkey vulture (Cathartes aura) migration decisions at both hourly and daily scales. Vulture movements in 10 migration events were ...recorded with satellite-reporting GPS sensors, and flight behavior was observed visually, aided by on-the-ground VHF radio-tracking. We used the North American Regional Reanalysis dataset to obtain values for wind speed, turbulent kinetic energy (TKE), and cloud height and used a digital elevation model for a measure of terrain ruggedness. A turkey vulture fitted with a heart-rate logger during 124 h of flight during 38 contiguous days showed only a small increase in mean heart rate as distance traveled per day increased, which suggests that, unlike flapping, soaring flight does not lead to greatly increased metabolic costs. Data from 10 migrations for 724 hourly segments and 152 daily segments showed that vultures depended heavily upon high levels of TKE in the atmospheric boundary layer to increase flight distances and maintain preferred bearings at both hourly and daily scales. We suggest how the MEM can be extended to other spatial and temporal scales of avian migration. Our success in relating model-derived atmospheric variables to migration indicates the potential of using regional reanalysis data, as here, and potentially other regional, higher-resolution, atmospheric models in predicting changing movement patterns of soaring birds under various scenarios of climate and land use change.
Understanding the movements of animals is pivotal for understanding their ecology and predicting their survival in the face of rapid global changes to climate, land use, and habitats, thus ...facilitating more effective habitat management. Migration by flying animals is an extreme form of movement that may be especially influenced by weather. With satellite telemetry studies, and the growing availability of information about the Earth's weather and land surface conditions, many data are collected that can advance our understanding about the mechanisms that shape migrations. We present the track annotation approach for movement data analysis using information about weather from the North American Reanalysis data set, a publicly available, regional, high-resolution model-observation hybrid product, and about topography, from a publicly available high-resolution digital elevation model (DEM). As a case study, we present the analysis of the response to environmental conditions in three contrasting populations of Turkey Vultures (
Cathartes aura
) across North America, tracked with a three-dimensional GPS-based sensor. Two populations in the east and west coasts of the United States responded similarly to weather, indicating use of both slope and thermal soaring. Continental-interior, "Plains populations," exhibited a different migratory pattern primarily indicative of thermal soaring. These differences help us understand the constraints and behaviors of soaring migrants. The track annotation approach allowed large-scale comparative study of movement in an important migratory species, and will enable similar studies at local to global scales.
Two major shortcomings of the US Endangered Species Act have led to inefficient use of conservation dollars: (1) it only provides conservation protection to distressed or rapidly declining species, ...and (2) it does not take full advantage of the market to reduce costs in conservation. New, derivativeâbased insurance products (financial instruments designed to allow the commoditization and sale of risk) have been developed that allow investors to insure risk in exchange for fixed payments. Modifications to these financial derivatives, which are used to distribute risk and stabilize forecasts across many corporate and social scenarios, could allow purchasers to take preventative action to simultaneously protect their investment and decrease the likelihood of the insured event. We propose that governments issue modified derivative contracts to sell species' extinction risk to market investors and stakeholders. Using the endangered redâcockaded woodpecker (Picoides borealis) in the US as an example, we show how a biodiversity derivatives program could proactively generate new funding, result in more costâeffective conservation, align stakeholders' interests, and create incentives for private conservation efforts.
SUMMARY
The effect of oral administration of THI, a compound present in ammonia caramel food colouring, was studied in spontaneous and induced murine diabetes mellitus. Continuous administration of ...THI at400 ppm in drinking water reduced the prevalence of spontaneous diabetes in female NOD/Lt mice from 63% in untreated controls to 8% in treated animals. Since cyclophosphamide (CP) accelerates and intensifies diabetes in NOD mice, we also studied the effect of THI in this model. Diabetes incidence was reduced from 100% in mice given only CP to 13–14% in mice given THI either concurrently or from 14 days previously. Histologically.THI greatly reduced the severity of insulitis. As measured by flow cytometry, all THI‐treated mice had a 60–80% reduction in splenic CD4+ and CD8+ T cells. THI‐treated mice showed no untoward effects and specifically no weight loss, or pathological changes in their livers, kidneys or lungs. However, there was moderate atrophy of the thymus cortex. THI is a small imidazole‐containing compound with structural similarity to histamine and urocanic acid, both known to have immunosuppressive properties. It is a widely used food additive with no known long‐term toxic effects al low dosage. Thus, THI could be a useful immunosuppressive agent.
As consensus grows regarding the unprecedented global environmental challenges we currently face, so too does the notion that publicly funded science has a duty to dedicate resources toward ...overcoming these challenges. In order for scientists to shift attention and resources to the most pressing global problems, we must first enumerate these issues and establish consensus across academia as to the importance and feasibility of solving them. To this end, we have applied concept mapping to a large and diverse pool of disciplinary experts â the entire faculty of Cornell University â to empirically assess their opinions on what our most pressing global crises are, how they relate to one another, and how feasible it would be to solve them. We (1) define what Cornell University faculty see as the most pressing problems of our day, (2) sort them into relevant, modern âdisciplinesâ, and (3) rate them according to both their importance and the feasibility of solving them. This study reveals broad consensus across disciplines, groups global crises into seven thematic clusters that cross disciplinary boundaries, and rates issues relevant to all disciplines on a scale of importance and solvability. We believe that this provides a structured framework for both the scientific community and the global community to address global crises.
Hip precautions are movement restrictions that are often advised following primary total hip arthroplasty (PTHA) for osteoarthritis (OA), but there is limited evidence supporting their effectiveness ...in preventing dislocation. This study aimed to explore the clinical reasoning behind the continuation and discontinuation of hip precautions following PTHA for OA.
Semi-structured interviews were conducted with therapists and surgeons at six centres using precautions and six centres not using precautions across secondary or tertiary NHS sites in England. Interviews were transcribed verbatim and thematically analysed.
Interviews were conducted with fourteen surgeons and eighteen therapists. Of these clinicians, eight surgeons and ten therapists routinely advised precautions. Clinicians continued to use precautions to avoid dislocation by creating a boundary to movement, particularly important when dealing with patients who "push" these boundaries. Clinicians discontinued precautions because of a perceived negative impact on patients and the lack of supporting evidence. In the absence of a rise in dislocation rates for these centres, others have now changed practice.
This study offers insight into the clinical reasoning behind the continuation and discontinuation of hip precautions following PTHA for OA. The use of precautions remains controversial and further work is required to determine whether or not they should be advised.
IMPLICATIONS FOR REHABILITATION
Redesign of future rehabilitation pathways for primary total hip arthroplasty should take into account viewpoints from across the multidisciplinary team to aid decision making.
Concern for patient behaviours, dislocation and litigation may be barriers to changing practice for rehabilitation after primary total hip arthroplasty.
Clinicians may be discontinuing hip precautions because of known surgical advances, a perceived negative impact on patients and a lack of supporting evidence for historical practice.
Individualised rehabilitation considerations are necessary for patients with risk factors that predispose them to dislocation after primary total hip arthroplasty, regardless of whether hip precautions are advised as standard at their given centre.
Behavioural side-bias occurs in many vertebrates, including birds as a result of hemispheric specialization and can be advantageous by improving response times to sudden stimuli and efficiency in ...multi-tasking. However, behavioural side-bias can lead to morphological asymmetries resulting in reduced performance for specific activities. For flying animals, wing asymmetry is particularly costly and it is unclear if behavioural side-biases will be expressed in flight; the benefits of quick response time afforded by side-biases must be balanced against the costs of less efficient flight due to the morphological asymmetry side-biases may incur. Thus, competing constraints could lead to context-dependent expression or suppression of side-bias in flight. In repeated flight trials through an outdoor tunnel with obstacles, tree swallows (Tachycineta bicolor) preferred larger openings, but we did not detect either individual or population-level side-biases. Thus, while observed behavioural side-biases during substrate-foraging and copulation are common in birds, we did not see such side-bias expressed in obstacle avoidance behaviour in flight. This finding highlights the importance of behavioural context for investigations of side-bias and hemispheric laterality and suggests both proximate and ultimate trade-offs between species-specific cognitive ecology and flight biomechanics.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The aim of this work was to study the role of the cell wall protein expansin in elongation growth. Expansins increase cell wall extensibility in vitro and are thought to be involved in cell ...elongation. Here, we studied the regulation of two tomato (Lycopersicon esculentum cv Moneymaker) expansin genes, LeExp2 and LeExp18, in rapidly expanding tissues. LeExp2 was strongly expressed in the elongation zone of hypocotyls and in the faster growing stem part during gravitropic stimulation. LeExp18 expression did not correlate with elongation growth. Exogenous application of hormones showed a substantial auxin-stimulation of LeExp2 mRNA in etiolated hypocotyls and a weaker auxin-stimulation of LeExp18 mRNA in stem tissue. Analysis of transcript accumulation revealed higher levels of LeExp2 and LeExp18 in light-treated, slow-growing tissue than in dark-treated, rapidly elongating tissue. Expansin protein levels and cell wall extension activities were similar in light- and dark-grown hypocotyl extracts. The results show a strong correlation between expansin gene expression and growth rate, but this correlation is not absolute. We conclude that elongation growth is likely to be controlled by expansin acting in concert with other factors that may limit growth under some physiological conditions.
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